From 6ea221519e0c726e28935a2e8d16d555027878ee Mon Sep 17 00:00:00 2001
From: Vivek Goyal <vgoyal@redhat.com>
Date: Thu, 19 May 2011 15:38:29 -0400
Subject: [PATCH] --- yaml --- r: 251159 b: refs/heads/master c:
 575969a0dd3fe65c6556bcb8f87c42303326ea55 h: refs/heads/master i:   251157:
 730f3610c2b973149c3cef2886b40744655e22dc   251155:
 e7d8ed992f031a80b8aa0de6546809fb27a0844b   251151:
 4a8cdebc14f356a5aac13699f5cebe9e2794662e v: v3

---
 [refs]                   |  2 +-
 trunk/block/blk-cgroup.c | 27 ++++++++++++++++++++++-----
 trunk/block/blk-cgroup.h |  2 ++
 3 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/[refs] b/[refs]
index f759c5210832..f5a3a4fb02ec 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 5624a4e445e2ec27582984b068d7bf7f127cee10
+refs/heads/master: 575969a0dd3fe65c6556bcb8f87c42303326ea55
diff --git a/trunk/block/blk-cgroup.c b/trunk/block/blk-cgroup.c
index 34bfcefdd924..3622518e1c23 100644
--- a/trunk/block/blk-cgroup.c
+++ b/trunk/block/blk-cgroup.c
@@ -400,14 +400,25 @@ void blkiocg_update_dispatch_stats(struct blkio_group *blkg,
 				uint64_t bytes, bool direction, bool sync)
 {
 	struct blkio_group_stats_cpu *stats_cpu;
+	unsigned long flags;
+
+	/*
+	 * Disabling interrupts to provide mutual exclusion between two
+	 * writes on same cpu. It probably is not needed for 64bit. Not
+	 * optimizing that case yet.
+	 */
+	local_irq_save(flags);
 
 	stats_cpu = this_cpu_ptr(blkg->stats_cpu);
 
+	u64_stats_update_begin(&stats_cpu->syncp);
 	stats_cpu->sectors += bytes >> 9;
 	blkio_add_stat(stats_cpu->stat_arr_cpu[BLKIO_STAT_CPU_SERVICED],
 			1, direction, sync);
 	blkio_add_stat(stats_cpu->stat_arr_cpu[BLKIO_STAT_CPU_SERVICE_BYTES],
 			bytes, direction, sync);
+	u64_stats_update_end(&stats_cpu->syncp);
+	local_irq_restore(flags);
 }
 EXPORT_SYMBOL_GPL(blkiocg_update_dispatch_stats);
 
@@ -622,15 +633,21 @@ static uint64_t blkio_read_stat_cpu(struct blkio_group *blkg,
 {
 	int cpu;
 	struct blkio_group_stats_cpu *stats_cpu;
-	uint64_t val = 0;
+	u64 val = 0, tval;
 
 	for_each_possible_cpu(cpu) {
+		unsigned int start;
 		stats_cpu  = per_cpu_ptr(blkg->stats_cpu, cpu);
 
-		if (type == BLKIO_STAT_CPU_SECTORS)
-			val += stats_cpu->sectors;
-		else
-			val += stats_cpu->stat_arr_cpu[type][sub_type];
+		do {
+			start = u64_stats_fetch_begin(&stats_cpu->syncp);
+			if (type == BLKIO_STAT_CPU_SECTORS)
+				tval = stats_cpu->sectors;
+			else
+				tval = stats_cpu->stat_arr_cpu[type][sub_type];
+		} while(u64_stats_fetch_retry(&stats_cpu->syncp, start));
+
+		val += tval;
 	}
 
 	return val;
diff --git a/trunk/block/blk-cgroup.h b/trunk/block/blk-cgroup.h
index fd730a24b491..262226798093 100644
--- a/trunk/block/blk-cgroup.h
+++ b/trunk/block/blk-cgroup.h
@@ -14,6 +14,7 @@
  */
 
 #include <linux/cgroup.h>
+#include <linux/u64_stats_sync.h>
 
 enum blkio_policy_id {
 	BLKIO_POLICY_PROP = 0,		/* Proportional Bandwidth division */
@@ -154,6 +155,7 @@ struct blkio_group_stats {
 struct blkio_group_stats_cpu {
 	uint64_t sectors;
 	uint64_t stat_arr_cpu[BLKIO_STAT_CPU_NR][BLKIO_STAT_TOTAL];
+	struct u64_stats_sync syncp;
 };
 
 struct blkio_group {